Portable electronic devices that have become greatly widespread in recent years are frequently used outdoors and therefore they need to be waterproof to some extent. In this respect, there is a suggestion that contributes to the realization of water resistance (see, for example, International Publication Pamphlet No. WO03/085793).
The above-mentioned document describes a process for producing a molded gasket that is a resin sealing member to be interposed between pieces of a housing when the housing is assembled. According to the invention proposed in this document, a part of a flexible flat cable (hereinafter referred to as “FCC”) is made integral with the gasket by pouring a resin into a mold after the FCC is disposed in the mold.
This type of gasket can be used, for example, in a folding portable telephone having a main unit with keys and a display unit with a display screen. In this example, the main unit and the display unit are each assembled, and a FFC partially integral with the gasket is used for communications between the main unit and the display unit. This makes it possible to prevent the entry of moisture into the portable telephone from a gap between the FFC and the gasket.
Incidentally, in late years, portable electronic devices such as portable telephones have become more sophisticated in functionality, requiring more signal lines than conventional devices. To keep up with this trend, it is conceivable to stack plural FCCs in the thickness direction. However, when the technique proposed in the above-mentioned document is employed for bonding the FFCs stacked in the thickness direction, it is necessary to carefully pour a resin to fill each space between the FCCs. Even if this careful filling is attempted, there are no guarantees that the resin can be appropriately poured to fill the space between the FCCs. When the filling of the resin is not appropriate, additional treatment for improving the sealing effect will be subsequently required, which makes the entire process complicated. In addition, use of a sealant requires such conditions that the sealant must be cured beforehand after being poured into the space between FCCs and the sealant needs to surely cover the entire width of the FCC, which is disadvantageous in terms of productivity.
In view of the above circumstances, it is an object of the present invention to provide a portable electronic device whose water resistance is improved by a simple method.